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OEM Spark Plug Gap.

Posted: Wed Apr 20, 2011 11:01 am
by Cougar Vibe
My gas mileage has recently taken a bit of hit on my '05 AWD, so amongst other things, I decided to install some new plugs and a new PCV. The plugs I went w/are the NGK Iridium IX ($28/AZ) and were gapped between 42-44 (about perfect). Anyway, I measured my old plugs to just see if any of them were really out of tolerance and here's what I got:Cyl. 1: .030 (?)2: .0373: .0404: .038It's been my experience that the gap expands over time due to erosion; but these plugs all come in below the .044 that I thought was OEM spec'd. Also, I'm really at a loss to explain the plug that came out of cylinder one (.030). BTW: Yes, I used two different gapping tools to check the tolerances.Thanks for any insight or comments.Cougar Vibe

Re: OEM Spark Plug Gap. (Cougar Vibe)

Posted: Wed Apr 20, 2011 12:50 pm
by star_deceiver
In some older carbbed vehicles with regular spark plugs you could narrow the gap to advance the timing and prolong regapping.The gaps you found were more likely from someone trying to gap them but not quite knowing what they were doing.

Posted: Wed Apr 20, 2011 1:54 pm
by Cougar Vibe
Yeah, I get the reason for closing the gap; I have a '66 Mustang that requires all sorts of tricks to keep it running smoothly based upon what season it is. That said, my Vibe's plugs are the OEM originals & I've never had my Vibe in for any work whatsover...so they either came mis-gapped from the NKG factory or something happened at NUMMI.

Re: (Cougar Vibe)

Posted: Wed Apr 20, 2011 2:35 pm
by star_deceiver
I suppose the plugs could have been fumbled while installing.... What numbers are on the OE plugs?